Describe Anne as a writer.

You need to consider that Anne was writing a diary, they were her personal thoughts and she did not mean them for a general audience. Still, we can see that Ann was introspective and had a talent with words. We can really see how she matures as a writer through the diary. 

We talked about the most private things, but we haven’t yet touched upon the things closest to my heart. I still can’t make head or tail of Peter. Is he superficial, or is it shyness that holds him back, even with me? But putting all that aside, I made one mistake: I used intimacy to get closer to him, and in doing so, I ruled out other forms of friendship.” 7/15/1944

Clearly we can see sophistication in her ideas and writing style.